Field of the Invention
The present invention relates to an image processing apparatus and an image processing method.
Description of the Related Art
Due to diffraction and an aberration generated in an image pickup optical system, light emitted from one point of an object has a minute spread without converging on one point. Distribution having such a minute spread is referred to as “a Point Spread Function (PSF)”. Due to the image pickup optical system, a shot image formed based on an object image convolved with the PSF is blurred and thereby deteriorates a resolution.
A shot image has been widely stored as electronic data, and a technique (hereinafter referred to as “an image restoration technique”) correcting image deterioration based on an optical system using image processing has been proposed. However, when an image where a resolution especially largely deteriorates is restored using the image processing, a correction quantity enlarges and noise data also increases with restoration processing. Accordingly, performing the restoration processing may be unfavorable depending on a noise quantity of an original image.
Japanese Patent No.5546229 discloses a correcting method that, of optical deteriorated information, a PTF (Phase Transfer Function) component is corrected using image restoration processing and a MTF (Modulation Transfer Function) is corrected using sharpness processing. Japanese Patent Laid-Open No.2009-033561 also discloses a method that constantly maintains a filter gain during an image restoration to constantly maintain a quality of an image corrected using image restoration processing and a method that changes a standard value for determining a quality according to a value of a restoration gain.
However, the method of Japanese Patent No.5546229 improves a phase component (PTF), but makes an amplitude component (MTF) dependent on the sharpness processing. Especially, in the case of an image having many noises, edge accuracy of detection lowers and thus a desired restoration effect is not obtained. Additionally, the method of Japanese Patent Laid-Open No.2009-033561 cannot obtain an optimum result with respect to an image imaged in various image pickup states liked an image imaged by a digital camera.